Zooming out makes image disappear in shader
This may have to do with the downsampling of the filter ('led-rgb') image.. I've made a node-group which makes the 'Trinitron' filter procedurally, instead:


By wrapping the scaled UV space into 0-1 cycles, it produces square UV tiles, 0-1 per tile. ('in-pixel UV')
By subtracting that from the smooth UV, we get a per-tile UV coordinate, at scale. That's scaled back down to an overall 0-1 to look up the color in the image(s). ('pixellated UV')
The 'in-pixel UV' X generates R,G and B strips per square tile, using the color ramp
The 'in-pixel UV' X,mod(1/3), and Y, are compared to 0 to generate black bars between the RGB strips, and the tiles. ('X Bar' and 'Y Bar')
The X Bars, Y Bars, and RGB strips are multiplied with the image to be depicted.

With this effect:

Used with solid green and red logos, it seems to stand up to Level-of-Detail resampling OK: